| hi there, common fault this is in the minis. But to save a trip to the dealer what I used to do in my old one was get a strip of velcro (the width of the window) and stick it to the seal. (the soft bit of the velcro not the hook bit)
Now you could not notice it at all, and it eliminated all of the noises from that part of the car!
Cheap and easy to do. grab some velcro from ebay! | 
